Scientists have discovered a new health benefit from the world's most consumed drink

The potential health benefits of tea have been widely reported but scientists have discovered another one to add to the list.

Tea leaves would act as a filter removing potentially harmful heavy metals like lead from water, according to a new study. 

Researchers from the United States tested different varieties of tea - green, black, oolong, white, chamomile, and rooibos - under typical brewing conditions with water containing known amounts of lead and other metals (chromium, copper, zinc, and cadmium).

Exposure to lead can lead to chronic health problems, with high doses causing brain and kidney damage in the most severe cases.

After brewing at 85 degrees Celsius, they evaluated how much of the metals were absorbed at different time intervals. 

Preparing a typical cup of tea could lead to a 15 per cent removal of lead from drinking water, according to the findings published in the journal ACS Food Science & Technology.

"[Tea leaves] have a high active surface area, which is a useful property for an adsorbent material and what makes tea leaves good at releasing flavour chemicals rapidly into your water," Benjamin Shindel, who was a PhD student at Northwestern University in the US and the study’s first author, said in a statement. 

He also highlighted the practicality of the process with tea being the most consumed beverage in the world with 6.5 million tonnes being consumed in 2022. 

"With tea, people don’t need to do anything extra. Just put the leaves in your water and steep them, and they naturally remove metals," he added. 

The transformation of tea leaves enhances their ability to bind with certain substances with black tea being slightly more effective than other varieties. 

Grinding the leaves also seems to amplify the effect, by enlarging the overall surface area that can capture metal.

Infusion time and bags are also factors

A longer brewing time was associated with a higher lead reduction, according to the results.

"Any tea that steeps for longer or has higher surface area will effectively remediate more heavy metals," Shindel said. 

"Brewing tea for longer periods or even overnight - like iced tea - will recover most of the metal or maybe even close to all of the metal in the water," he added.

Researchers also observed that the presence of a tea bag was a contributing factor in the process. 

Cellulose bags, made from wood pulp, were the most effective in trapping metal ions. 

"The cotton and nylon bags remove practically no heavy metals from water," Shindel said.

"Nylon tea bags are already problematic because they release microplastics, but the majority of tea bags used today are made from natural materials, such as cellulose. These may release micro-particles of cellulose, but that’s just fiber which our body can handle".

These filtration properties can be added to the list of benefits associated with tea consumption, such as enhanced cardiovascular health and a protective effect against neurodegenerative diseases.

"Across a population, if people drink an extra cup of tea per day, maybe over time we’d see declines in illnesses that are closely correlated with exposure to heavy metals," he said.